不同放牧强度下羊草和大针茅草原土壤含水量的空间变化

摘要

近年来不合理的放牧体制造成内蒙古地区土壤退化严重.基于内蒙古草原生态系统研究站建立围封(UG79)、冬季放牧(WG)、持续放牧(CG)和过度放牧(HG)条件下羊草(Leymus chinensis)和大针茅(Stipa grandis)草原试验区研究不同放牧强度和植被覆盖条件下土壤含水量的空间变化.试验共分为5个小区,分布为:LUG79、LWG、LHG、SUG79和SCG.试验利用GPS在每个小区建立1个长135 m,宽105 m,共计100个测量点的空间区域,通过利用HH2 Moisture Meter测量土含水量并研究其空间变化情况.结果表明:降水是引起区域土壤含水量变化的主要因素,是引起土壤含水量空间变异的关键因子.在羊草区,LWG土壤含水量(0.29~0.05 cm3·cm-3)高于LUG79(0.24~0.03 cm3·cm-3),而LHG由于过度放牧导致最小的土壤含水量(0.21~0.01 cm3·cm-3).在大针茅区SCG土壤含水量(0.28~0.07 cm3·cm-3)要大于SUG79区(0.27~0.05 cm3·cm-3).相较于围封而言,SCG和LWG区在适度的持续放牧与冬季放牧方式下能增强土壤对水分的保持能力,说明适度的放牧强度能增加土壤含水量.在围封区域 SUG79 区的土壤含水量高于 LUG79 区的土壤含水量.从地统计分析结果看,每个试验区的土壤含水量空间分布均具有一定的稳定性,其空间结构比均高于97%.但两个围封的UG79区土壤含水量空间分布比放牧的CG、WG和HG试验区更稳定,说明放牧对土壤含水量空间分布的稳定性有一定破坏作用.%The improper grazing manner led to soil deterioration in Inner Mongolia grassland. To understand the change of soil water content and its' spatial distribution, 5 plots: Un-grazed since 1979 (LUG79), winter grazing (LWG) and heavy grazing (LHG) under Leymus Chinensis (L), and Un-grazed since 1979 (SUG79) and continuous grazing (SCG), underStipa Grandis(S) Grassland were investigated by HH2 Moisture Meter. In each plot, a regular sampling grid which covered an area of 105m×135m and included 100 points was positioned by GPS. The results showed that precipitation is the key factor to change the magnitude and the spatial variability and distribution of soil water content in Inner Mongolia Grassland. UnderLeymus Chinensis plots, soil water content was greater in LWG (0.29~0.05 cm3·cm-3) than LUG79 (0.24~0.03 cm3·cm-3), however the value was lowest in LHG (0.21~0.01 cm3·cm-3). UnderStipa Grandis the soil water content was greater in SCG (0.28~0.07 cm3·cm-3) than in SUG79 (0.27~0.05 cm3·cm-3). Comparing to un-grazing plots, SCG and LWG could increase the soil water content due to appropriate continuous grazing and winter grazing. In 2 un-grazing plots the soil water content was greater in SUG79 than in LUG79. The geostatistical analyst showed the Proportion for the spatial distribution of soil water content were over 97% in all plots but they were more stable in UG79 than other grazing plots, which indicated grazing destroyed the distribution at some extent.